You're coming along a treat with this.
Here's a sneaky hint for you:
1. Open your page in Arachnophilia
2. Click on Tools, go down to Beautify and select Analyze HTML or just click on Ctrl+L
3. Click on the top right button on the resulting dialog panel called Beautify (use all tags) the follow all prompts to analyze the page code.
Note, Arachnophilia does not always get this right so be careful how you use it, but it can and does help.
Keep in mind that here are more ways to create an HTML page than you can shake a stick at and 'correct' code can consist of very different tags to get a similar visual page. What I'm getting at here is that there are several correct ways of acheiving the desired results, just as there are many ways of making mistakes.
If you want a real scare, look at your pages in alternative browsers. NetScape and Firebird overlapped some text with table borders and got one or two other things wrong...
Finally, if you really want to frighten yourself, use the excellent W3C Markup Validation Serive click here
You'll see what I mean when I say there are more ways of creating a page and getting it right, or wrong.
Good luck with it.